Yes, lightning is 5 times hotter than the surface of the sun. Lightning can reach temperatures of 30,000 degree Kelvins(53,540 degree fahrenheit) whereas the surface of the sun has temperature of 6000 degree Kelvins(10,340 degree Fahrenheit. But we are only talking about the surface of the sun which is it's coolest layer. Digging into the core of the sun, you will find temperatures of 15 Million Kelvins(nearly 27 Million Fahrenheits). Lightning is actually a movement of charges which does not have a temperature. But the resistance of the movements of such large amount of charges causes the surrounding to heat up. Studies show that good conductors of heat do not heat up as much as poor conductors of heat. Air, which is a really poor conductor of electricity reaches temperatures of about 50,000 Fahrenheits when lightning passes through it.